The Accretion Disk Limit Cycle Mechanism: Constraints on the Low State
Session 52 -- Interacting Binaries: Accretion Phenomena
Display presentation, Thursday, January 13, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[52.03] The Accretion Disk Limit Cycle Mechanism: Constraints on the Low State

John K. Cannizzo (NASA/GSFC)

The accretion disk limit cycle mechanism was developed to account for the dwarf nova outbursts. In this model there exists a hysteresis relation between local accretion rate and surface density within the disk. The basic mechanism should also apply in a variety of other systems containing disks. We utilize a time dependent accretion disk code to examine the dependence of outburst properties in the limit cycle model on the input physics for the quiescent state. In particular, we study the effects of (1) varying the slope of the lower branch of the S-curve, $b_1 = d\ln T_{\rm effective}/d\ln\Sigma$, and, (2) the depletion of the inner disk edge by magnetic fields and coronal siphon flow. Several characteristics of the outbursts depend critically on these pieces of physics. In particular, the depletion of the disk causes outbursts to begin at larger radii in the disk, as does a larger value of $b_1$. Furthermore, the recurrence time for bursts starting at large radii shows more dependence on variations in the mass transfer rate into the outer edge of the accretion disk.

This work was supported by the National Academy of Sciences through an NRC associateship at Goddard Space Flight Center.